Field of the Invention
This invention relates generally to a tire tread. More specifically, this invention relates to tire treads for heavy trucks, in particular tires for free-rolling wheels thereof (so called steer positions and trailer positions), especially tires for steer positions.
Description of the Related Art
Tire treads generally extend about the outer circumference of a tire to operate as the intermediary between the tire and a surface upon which it travels (the operating surface). Contact between the tire tread and the operating surface occurs along a footprint of the tire. Tire treads provide grip to resist tire slip that may result during tire acceleration, braking, and/or cornering. Tire treads may also include tread elements, such as ribs or lugs, and tread features, such as grooves and sipes, each of which may assist in providing target tire performance when a tire is operating under particular conditions. The tread pattern generally includes repetitions of identical sub-patterns, the length of such sub-pattern being referred to as the “pitch”. Each rib (seen in isolation) may have its own pitch and this pitch may be different from the pitch of the full tread including all tread elements and features.
One common problem faced by tire manufacturers is how to increase the wear resistance of treads and further reduce the rolling resistance of tires.
A solution is to increase the ratio of the tread surface being in contact with the operating surface. This ratio is known as the Contact Surface Ratio (CSR). Increasing the CSR is known to be beneficial for wear life and can be beneficial for rolling resistance too. However, increasing the CSR is also known for harming the wet braking adherence performance of the tread. Wet braking adherence performance being a very important element, this trade-off may not be acceptable.
Irregular wear is also a great concern as it can provoke vibrations that become sensible by the driver in the steering wheel or a poor looking wear pattern, both of which leading to the tire being often removed from service at an early stage of its wear life.
Therefore, to reduce the rolling resistance of tires it may be desirous to propose a novel way to design tire treads that would not result in compromising their wet braking performance or the wear life of the tread.